Lacquer formulation



United States Patent 4 LACQUER FORMULATION Henry C. Pospychala and Garrett H. Peters, Rhinelander,

Wis., assignors to Rhinelander Paper Company, Rhinelander, Wis., a corporation of Wisconsin No Drawing. Application July 14, 1953, Serial No. 367,996

8 Claims. (Cl. 106-173) Our invention relates to paper coating, and more particularly, to an improved lacquer or paper coating composition, to an improved process of applying the same to paper, and to an improved coatedpaper resulting therefrom.

Although a great number of paper coating compositions have been suggested for one purpose or another, and certain coating compositions are clearly superior for coating one type of paper although inferior for coating another type, there is a continuing need for certain particular types of improved coatings for certain particular types of paper. The instant invention relates to a coating composition that is uniquely suitable for coating substantially all types of paper, but it is particularly suitable for the coating of glassine paper. The instant lacquer or coating composition when properly applied and dried will give superior gloss and transparency, heat sealing, resistance to blocking (tack or stickiness), hot slip and cold slip properties, and in addition, superior resistance to water vapor penetration. Nitrocellulose lacquers have been used for some time in the coating of paper and the like cellulose sheet material, but a particularly significant deficiency in these coatings is their relatively poor resistance to Water vapor penetration. The instant invention pertains to a combination of coating ingredients which cooperate to obtain a synergistic effect in the coating of paper.

It is, therefore, an important object of the instant invention to provide an improved lacquer or coating composition, an improved method of applying a lacquer or coating composition to paper, and an improved coated paper resulting therefrom.

It is another object of the instant invention to provide an improved coating composition consisting essentially of cellulose nitrate, ester gum resin, a plasticizer, and wax.

It is a further object of the instant invention to provide an improved lacquer comprising a volatile quick-drying hydrocarbon-ester-alcohol solvent having intimately dis persed therein, in amounts from to 100 percent thereof, solids consisting .essentially. of low nitrogen type cellulose nitrate, ester gum resin, an alkylaryl phosphate plasticizer, paraflin wax and carnauba wax.

' Still another object of the instant invention is to provide an improved paper sheeting having a lacquer film deposited equally on both sides of the sheet, for improving its gloss and resistance to water vapor penetration, said film consisting essentially of cellulose nitrate, ester gum resin, a plasticizer, and wax.

Yet another object of the instant invention'is to provide an improved process of coating paper that comprises applying thereto a lacquer comprising a volatile quickdrying hydrocarbon-ester-alcohol solvent having intimately dispersed th ereimin amounts from 5 to 100 percent thereof, solids consisting essentially of cellulose nitrate, ester gum resin,'a plasticizer, paraffin Wax and 2,793,959 Patented May 28,

carnauba wax; and subjecting the coated paper to evaporation conditions to remove the solvent therefrom and dry the solids film thereon.

Other objects, features and advantages of the instant invention will become apparent to those skilled in the art from the following detailed disclosure of preferred em bodiments thereof."

In its more specific aspects'the invention consists in a coating compositionconsisting essentially of 42 to 46 parts of low nitrogen type cellulose nitrate, 34 to 39 parts of 2-ethylhexyl diphenyl phosphate, 17 to 22 parts of glycerol-rosin-maleate, 2 to 5' parts 'ofparaflin wax, and not more than 1 part of carnauba wax; and a lacquer solution of such compositionin a solvent mixture of 35-65 volume percent ethyl acetate, 10-30 volume percent ethyl alcohol and 20-40 volume percent toluol; and a-proce'ss of coating paper therewith and the paper sheeting-resulting after the coating thereof.

The instantcoating composition, or the so called solids portion thereof which is initially dissolved or dispersed in the solvent and is subsequently deposited as a film upon the paper, is essentially a cellulose nitrate base coating. Although other cellulose esters may be used, perhaps in combination with cellulose nitrate, it has been found that theinstant combination of materials produces uniquely superior results using a cellulose ester base that consists almost entirely of cellulose nitrate. Moreover, it has been found that the low nitrogen type cellulose nitrates (i. e., about 11, or 10.7 to 11.2% nitrogen content) give superior results-in the practice of the invention (but up'to 11.8-12.2% may be used). i Another essential ingredient of the instant coating com position isthe so called rriodified, ester gum or ester, gum resin, as used herein; Any'of the various compatible resins of this class may be used, but the most preferred is ester gum resin. As is known,-abietic acid has a single unsaturation in its structure which is capable of reacting with the unsaturation in the maleic acid structure, and in these maleic acid modified ester gums, the maleic acid and the abietic acid of the rosin are joined through these unsaturations, so as to form a trivalent organic acid radical which is neutralized with a polyhydric alcohol such as glycerol or pentaerythritol to yield the resulting ester gum resin. In the use of glycerol-as the polyhydric alcohol, the resulting product is glycerolrosin-maleate, which is preferred for use in the instantinvention.

In general, the cellulose nitrate and the ester gum resin are used in combination so as to obtain the desired hard-- ness and gloss in the resultingfilm on the paper sheet. The preferred ratio is about 1 part of cellulose nitrate for /s to /2 part of the ester gum resin.

Another essential ingredient of the instant coating composition is the plasticizer, which is used as the name indicates in the amounts necessary to sufiiciently plasticize the cellulose nitrate, in particular, as well as the combination of cellulose nitrate and ester gum resin. To a certain extent at least, plasticization is carried out to obtain a desired texture, hardness, etc. In the instant invention, however, it has been found that the amount of plasticizer employed is quite critical and superior r esults are obtained only by the use of plasticizer. within certain relatively narrow limits. In general, the amount of plasticizer used should be 0.7 to 0.9 part per-part of: cellulose nitrate. (As used herein, the terms parts and percent mean parts and percent by weight, unlesso'ther'f wise designated.) i

"The plasticizer nsed in' the instant invention is-pre'fer; ably an alkyl-aryl phosphate plasticize'r i, e. an 'a-Ikyl f' diphenyl phosphate .plasticizer having the formula:

and most preferably it is Z-ethylhexyl diphenyl phossha Still another essential ingredient used in the instant coating composition is wax. The amount of wax used is relatively small so as not to harmful'ly affect or completely alter the properties of the cellulose nitrate-ester gum maleate plasticized composition. On the other hand, the presence of the wax is of essential importance inconnection with such properties as heat sealing, resistance to blocking, hot .slip and cold slip properties and resistance to water vapor penetration. Moreover, it has been found that parafiin .wax is preferred, at least as the primary or predominating wax component in the wax. Other Waxes may be admixed with the paraffin wax, if desired; however, it has been found that the paraffin wax should comprise at least about 80% of the wax used. The total amount of wax used may range from about 1 to parts per 40 parts of cellulose nitrate.

As another aspect of the instant invention, it has been found particularly advantageous to include a small amount of carnauba wax with the paraflin wax in the instant coating composition. The carnauba wax imparts superior anti-blocking properties to the composition on good grade glassine paper. The amount of carnauba wax used may be as high as 1 part per 40 parts of cellulose nitrate, although it is usually not desirable to use more than about 1 part and preferably about /2 part is employ d.

As a typical example of a preferred embodiment of the invention, the following formulation is submitted:

Preferred Most Pre- Proportions erred Ingredients (Parts) (Parts) 4246 44 Cellulose nitrate.

34-39 36 2-ethylhexy1 diphenyl phosphate. 17- 22 20 glycerol-rosin-In aleate.

2- 5 3 palgafiiu wax,(M. P. 145

0.25425 0. 5 carnauba wax.

This formulation of solids is intimately dispersed (and preferably completely dissolved) in a volatile quickdrying hydrocarbon-ester-alcohol solvent to form a coating lacquer. The solids content thereof is from about 5 to about 100% of the solvent, and preferably 50% As an example of the method of the instant invention, a 25% solids lacquer solution, using solids of 44 parts of cellulose nitrate, 36 parts of 2-ethylhexyl diphenyl phosphate (i. e. Santicizer #141); 20 parts of glycerolrosin-maleate (i. e. Amberol 801) and 3 parts of paraffin wax, and using a solvent of 48 vol. percent ethyl acetate, 20 vol. percent ethyl alcohol and 32 vol. percent toluol, is coa e o t opposi e des o g o grad vslassine pap in amounts sufi icient ,to coat the paper with 3% pounds film per ream (3000 square feet of paper) deposited equally on both sides. This is an application of 3% pounds of film to 6000 square feet of paper surface. The coated paper is next dried by heating under evaporation conditions at about 80 .C. (and preferably a temperature at least above 50-65" C., the melting point of the wax).

The water vapor penetration of the resulting coated glassine paper is 0.2 to 0.4 gram (per 100 squareinches) in 24 hours under conditions of 100 .F. and 9.0% humidity on one side and 0% humidity (atmosphere over dry calcium chloride) on :the other side, thereby indicating a distinctly superior water vapor penetration resistance.

It is further noted that the resulting coated glassine paper has unusually good gloss and transparency, excellent heat scaling properties, good resistance to blocking,

(and preferably 3 to 3 /2 pounds) of solids or lacquer good hot slip and cold slip properties, and generally superior properties for coated good grade glassine paper.

Actually, the amount of solids in the solvent may be varied appreciably without harmful effect on the performance of the deposited film. It is preferable, however, to employ drying temperatures above the melting point of the Wax in order to obtain maximum uniformity and homogeneity in the deposited film.

It is also possible to employ different hydrocarbonester-alcohol solvent mixtures. Essentially, the ethyl acetate is an active solvent for the cellulose nitrate, but other esters may be used such ,as propyl acetate and butyl acetate. The hydrocarbon (toluol) is used primarily for an inexpensive diluent for the resin solution and other suitable hydrocarbons may be used although preferably the hydrocarbons are aromatic hydrocarbons such as toluol and xylol. The alcohol (ethyl alcohol) is usually present in the cellulose nitrate and its presence materially assists in the quickdrying properties of the lacquer, although other alcohols such as methyl and propyl alcohol may also be used. The ester and alcohol contents may in each case be as low as 5 vol. percent for purposes of economy.

If the above formulation is modified by the addition of 1 part of carnauba wax to the solids, it is found that the water vapor penetration is increased to as much as 0.5 gram (although still a superior result) and the antiblocking properties of the coated paper are noticeably improved.

Comparable results are obtained using as little as 4 grams to the square meter i. e. one pound per ream of the lacquer film .on plain transparent cellophane; but substantially greater amounts (such as 4.5 to 6 pounds per ream) must be 'used to obtain good heat-sealing and water vapor penetration resistance on low grade 'glassines or other more absorbent papers. Also, the superior results of the invention maybe obtained by coating only one side of the paper with the instant composition.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. A lacquer comprising a volatile quick-drying solvent mixture of 35-65 volume percent ethyl acetate, 10-30 volume percent ethyl alcohol and 20-40 volume percent toluol having dissolved therein from 10 to 50 Weight percent of a coating composition consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of Z-ethylhexyl di phenyl phosphate, 17 to 22 parts of glycerol-rosin-maleate, 2 to 5 parts of paraflin wax, and not more than 1% part of carnauba Wax.

2. Glassine paper coated with 3 to 3 /2 pounds of a lacquer film per 3000 square feet of paper, deposited equally on both sides thereof for improving its gloss, transparency and resistance to water vapor penetration, said film consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of Z-ethylhexyl diphenyl phosphate, 17 to 22 parts of glycerol-rosin-maleate, 2 to 5 parts of paraffin wax, and not more than 1% parts of carnauba wax.

3. A lacquer comprising a volatile quick-drying solvent having dissolved therein from to 50 weight percent of a coating composition consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of 2-ethylhexyl diphenyl phosphate, 17 to 22 parts of glycerolrosin-maleate, and 2 to 5 parts of parafiin wax.

4. A lacquer comprising a volatile quick-drying solvent mixture of 35-65 volume percent ethyl acetate, 10-30 volume percent ethyl alcohol and 20-40 volume percent toluol having dissolved therein from 10 to 50 weight percent of a coating composition consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of an alkyl diphenyl phosphate plasticizer having the formula:

/0 alkyl-O-P alkyl-O-P 17 to 22 parts of glycerol-rosin-maleate, and 2 to 5 parts of parafiin wax.

6. Glassine paper coated with 1 to 6 pounds of a lacquer film per 3000 square feet of paper for improving its gloss, transparency and resistance to water vapor penetration, said film consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of 2-ethylhexyl diphenyl phosphate, 17 to 22 parts of glycerol-rosinmaleate, 2 to 5 parts of parafiin wax, and not more than 1% parts of carnauba wax.

7. Glassine paper coated with 1 to 6 pounds of lacquer film per 3000 square feet of paper for improving its gloss, transparency and resistance to water vapor penetration, said film consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of 2-ethy1hexyl diphenyl phosphate, 17 to 22 parts of glycerol-rosin-maleate, and 2 to 5 parts of paraffin wax.

8. Paper coated with 1 to 6 pounds of lacquer film per 3000 square feet of paper for improving its gloss, transparency and resistance to water vapor penetration, said film consisting essentially of 42 to 46 parts of cellulose nitrate, 34 to 39 parts of an alkyl diphenyl phosphate plasticizer having the formula:

17 to 22 parts of glycerol-rosin-maleate, and 2 to 5 parts of paraflin wax.

References Cited in the file of this patent UNITED STATES PATENTS 1,896,215 Bradley Feb. 7, 1933 2,349,134 Bradshaw May 16, 1944 2,379,974 Little May 16, 1944 

4. A LACQUER COMPRISING A VOLATILE QUICK-DRYING SOLVENT MIXTURE OF 35-36 VOLUME PERCENT ETHYL ACETATE, 10-30 VOLUME PERCENT ETHYL ALCOHOL AND 20-40 VOLUME PERCENT TOLUOL HAVING DISSOLVED THEREIN FROM 10 TO 50 WEIGHT PERCENT OF A COATING COMPOSITION CONSISTING ESSENTIALLY OF 42 TO 46 PARTS OF CELLULOSE NITRATE, 34 TO 39 PARTS OF AN ALKYL DIPHENYL PHOSPHATE PLASTICIZER HAVING THE FORMULA: 